Generally, digital multimedia broadcasting (DMB) refers to a broadcasting service for providing various multimedia data and signals, such as high-quality voice and image data, in a digital manner to a device having a DMB receiver, even when the device is mobile. Examples of such a device include a personal digital assistant (PDA), a terminal for a vehicle and a mobile terminal. The DMB may be divided into a terrestrial DMB (TDMB) and a satellite DMB (SDMB) according to how signals including digital broadcasting data are transmitted.
According to the TDMB, a user may receive airwave broadcasts free of charge without an additional subscription procedure because the TDMB does not provide for requirements or specifications for conditional access. Thus, the TDMB does not practice providing specific pay broadcast services to limited users based on conditional access.
On the contrary, the SDMB implements paid broadcast services and provides various high-quality image data, audio data, or broadcasting data through specified DMB channels. That is, a satellite broadcast or a cable broadcast activates pay subscribers or pay channels to allow corresponding subscribers to receive corresponding broadcast services. In that case, broadcast signals that were converted into an encrypted format by a conditional access system (CAS) can be restored back to its original state using an appropriate device, such as a set-top box. The restoration function is applied to the SDMB, thus a SDMB receiver is provided with functions related to the CAS therein.
However, attempts to include the functions related to the CAS into a TDMB receiver has been problematic. For example, a large memory capacity is necessary, and a dedicated application (software, hardware, and/or a combination thereof) is to be developed. Also, a booting system (software, hardware, and/or a combination thereof) is to be designed to provide security. Accordingly, the functions related to the CAS, as applied to the SDMB receiver, cannot be integrally applied to the TDMB receiver.
Moreover, the related art TDMB, which practices free-of-charge broadcasting, does not provide a specification for conditional access. Hence, the TDMB does not consider a demand for transmitting or receiving high-quality broadcasts. In an attempt to solve the problem, the CAS of the SDMB was applied to the TDMB. However, the result was unfavorable because an expensive dedicated system being applied to the TDMB receiver through a complicated design modification was required.